A thin film magnetic head for use in a magnetic disc apparatus or the like is formed of a component obtained by processing a bar-shaped ceramic (hereinafter referred to as a “ceramic bar”) on the surface of which are formed a large number of element portions consisting of magnetic thin films or the like forming induction type magnetic conversion elements that are electro-magnetic conversion elements, magnetic resistance elements (hereinafter referred to as “MR elements”) that are magneto-electric conversion elements, etc. A large number of such element portions are first formed simultaneously on a wafer-shaped ceramic substrate, which is cut in one direction into a bar shape to thereby obtain the above-mentioned ceramic bar.
A large number of such element portions are simultaneously formed on a wafer-shaped ceramic substrate by using a thin film forming and processing technique, such as a semiconductor manufacturing technique. In this process, film formation, photo resist application, exposure of wiring configuration, etc., removal of photo resist in the exposure portion, etc. are performed on the respective thin films for magnetic resistance measurement, magnetic poles, coils, insulation, etc. Thereafter, a protective film is formed in the uppermost portion to complete the formation of the element portions.
Further, on the ceramic bar on which a plurality of element portions have been formed, a processing, such as lapping, is performed so as to adjust the throat height, MR height, etc. of each element portion to an appropriate value. Generally speaking, to stabilize the output characteristics of a magnetic head in a magnetic disc apparatus, it is necessary to maintain an extremely small fixed distance between the magnetic pole portion of the magnetic head and the surface of the recording medium, and the throat height or MR height is an important parameter in determining this distance.
After a predetermined throat height, etc. have been obtained in each element portion, further performed on this lapped surface are a rounding processing for forming the lapping surface into a curved surface having a predetermined radius of curvature, a processing for forming a groove for the lapping surface, a processing for lapping an end portion to form a surface inclined with respect to the lapping surface, etc. In the subsequent process, the ceramic bar is individually separated into the respective element portions, each constituting a component of a magnetic head for a magnetic disc apparatus. When the magnetic head is used in a magnetic disc apparatus, and performs the recording and reproduction of a magnetic signal on and from a magnetic disc, this component constitutes a slider whose ceramic portion flies over the magnetic disc by the air pressure due to the rotation of the disc, and the element portion constitutes a head core which performs the recording and/or reproduction of the magnetic signal of the disc.
The term “throat height” means the length (height) of the magnetic pole forward end portion of such a head core for performing the recording and reproduction of the magnetic signal, where two magnetic poles are opposed to each other with a minute gap therebetween. The term “MR height” means the distance (height) between the end portion of the MR element opposed to the medium and the end portion thereof on the other side. To enable a signal to be appropriately recorded and reproduced, it is necessary for the values of the throat height and the MR height to be predetermined ones. To obtain the predetermined values, high accuracy in lapping is required.
Further, as stated above, due to the pressure of the air flow generated as a result of the high speed rotation of the disc, the slider flies over the disc surface, while being separated therefrom by a minute distance. To accurately perform the writing of information on the disc and the reading of information from the disc by the element portion, it is necessary for the flying height of the flying slider and the attitude of the slider at the time of flying to be always stable. By performing the above-mentioned rounding processing, etc. on the slider, it is possible for the slider to fly in a stable manner.
However, generally speaking, due to the stress, etc. generated as a result of the cutting from the ceramic substrate or the formation of the element portions, the ceramic bar involves distortion, bending, etc., so that it is difficult to achieve such a high processing accuracy as mentioned above solely by securing the ceramic bar and performing lapping thereon. In view of this, instead of an ordinary lapping apparatus, there has been proposed an apparatus which makes it possible to lap a magnetic head while in the form of a ceramic bar with high accuracy as disclosed, for example, in U.S. Pat. No. 5,620,356. The applicant of the present application has also proposed a number of such apparatuses and methods (Japanese Patent Application No. 11-162799, etc.). A method of processing a ceramic bar to obtain a predetermined throat height, etc. will be described. First, the surface of the ceramic bar on the opposite side of the surface to be lapped is glued to a jig by an adhesive or the like, and the surface of the ceramic bar to be lapped is pressed against the lapping surface of a lapping table through the intermdiation of the jig to thereby lap the surface to be lapped. By receiving a load, etc. from outside, the portion of this jig holding the ceramic bar undergoes the deformation, causing the ceramic bar to be deformed at the same time. Due to this arrangement, it is possible to correct the bending, etc. of the ceramic bar itself.
It is also possible to perform the above-mentioned rounding processing, etc. by using the method or the apparatus used in the method. Actually, however, due to the construction of the apparatus, it is difficult to obtain a smoothly rounded configuration, so that, generally, the rounding processing, etc. are performed by using an apparatus different from such apparatuses. Of the rounded configurations, a configuration in which the central portion of a lapped surface protrudes, or a configuration in which the lapped surface constitutes a part of a spherical surface, is referred to, in particular, as a crown configuration, and the processing for obtaining a crown configuration is called a crown processing. The applicant of the present application has proposed in, for example, Japanese Patent Application No. 11-302305, a lapping apparatus and a lapping method for performing a crown processing on the sliders while in the form of a ceramic bar.
The method for performing the crown processing on a ceramic bar disclosed by the present applicant will be described. The lapping surface of a lapping table formed of tin or the like used for the lapping of a ceramic bar is formed as a substantially concave conical shape constituting a part of a sphere having a predetermined radius. During the lapping, the ceramic bar is held by a horizontal jig extending in the longitudinal direction of the ceramic bar. Specifically, the surface of the ceramic bar on the opposite side of the surface to be lapped is attracted by an elastic member such as a rubber plate glued to one end surface of the horizontal jig by an adhesive, whereby the ceramic bar is held by the end surface of the jig.
By applying a load to the central portion of the jig so as to press the ceramic bar against the lapping surface, the entire surface to be lapped of the ceramic bar is lapped, forming the surface to be lapped into a crown-shaped configuration. At the same time, an appropriate load is applied to either end of the ceramic bar, whereby the longitudinal variation in the crown configuration formed on the ceramic bar is mitigated. Further, through an electrode or the like formed on the jig, the MR value of the MR element formed on the ceramic bar is measured during the lapping, and the load for pressing the ceramic bar against the lapping surface is controlled on the basis of the measurement result, whereby the lapping amount at the time of crown processing is controlled.